The standard approach [1]} is to consider the limiting case of infinite volume, \(V \rightarrow \infty \) , and infinite number of particles, \(N \rightarrow \infty \) , keeping the particle density constant, \(N/V \rightarrow \rm {const}\) .
It is known, that in such a limit, BEC forms in the 3D case and does not form in the 2D case.
